The present invention relates to a disk cartridge containing an optical disk for use as a recording medium, and more particularly, to a disk cartridge provided with a shutter capable of sliding in two opposite directions.
These days, 90 mm optical disks of a magnetooptic (MO) recording type are widely used as large-capacity recording media that replace floppy disks. Recently, moreover, there have been developed 90 mm reloadable optical disks of a phase-change (PC) type that are double-sided and can enjoy a larger capacity, and optical disk drives that are furnished with these optical disks.
The basic dimensions of a PC-type optical disk, including the longitudinal and transverse dimensions, are identical with those of a 90 mm MO-type disk. In order to make the most of the features of the disk of this type, however, the disk is provided with an exclusive-use cartridge that is characterized by its thickness and a unique shutter sliding mechanism.
In general, a disk cartridge comprises a flat rectangular casing that contains an optical disk therein. The casing has a window section on each side thereof, through which a part of the optical disk and a hub are exposed. The casing is provided with a slidable shutter for opening and closing the window sections.
Recently proposed disk cartridges of this type are described in Jpn. Pat. Appln. KOKAI Publication Nos. 63-119081 and 63-94487, for example. These cartridges are of a two-way shutter type, and are provided with a shutter that can slide on either side of the window sections.
One such disk cartridge of the two-way shutter type comprises a pair of shutter springs that are arranged on either side of the shutter, and the shutter is held by means of the shutter springs in a closed position where it closes the window sections. Each shutter spring has one end fixed to the casing and the other end fixed to the shutter. Further, the shutter is formed having two apertures that are spaced as desired. As the shutter is slid in one direction, resisting the urging force of one shutter spring, one of the apertures of the shutter is opposed to its corresponding window section, thereby allowing the window section to open.
Further, there is provided a two-way-shutter disk cartridge of another type, which comprises a guide shaft extending across the width of a casing, a pair of sliders slidably mounted on the guide shaft, a tension spring connecting the sliders to each other, and a protrusion formed on the inner surface of the casing so as to restrain the sliding motion of each slider.
In sliding the shutter of this disk cartridge in one direction, one of the sliders move together with the shutter on the guide shaft, while the other slider is restrained from moving in the one direction by the protrusion. Thereupon, the shutter moves to its open position under the urging force of the tension spring. When the shutter is released from a force to slide it in the direction to open the window sections of the casing, it is returned by means of the urging force of the tension spring to its closed position where it closes the window sections.
According to the foregoing disk cartridge having the pair of shutter springs, however, it is difficult to hold the shutter accurately in the closed position, due to variation in the urging force of the shutter springs and the like. Since each shutter spring extends or contracts as the shutter is slid to open the window sections, moreover, the shutter cannot enjoy a generous movement stroke.
On the other hand, the disk cartridge that is provided with the guide shaft, sliders, etc. includes so many components that its manufacturing cost is high, and its structure is too complicated to be assembled with ease. Thus, the disk cartridge of this type is not suited for automatic assembly in mass production, in particular.
Meanwhile, it has been ten years or more since music compact disks were first developed, and read-only optical disks (hereinafter referred to as ROM-type disks) of various kinds, represented by CD-ROMs, photo-CDs, etc. for personal computers, have been developed and widely used for business or public use. Besides these ROM-type disks, there have recently been developed ROM-type disks (CD-R) that permit writing of data only once and recording/reproducing disks (hereinafter referred to as RAM-type disks) that permit repeated recording and erasure. As a result, optical disks of ten kinds or more are commercially available.
For economic reasons or due to restrictions on the manipulation of drive units, necessity to secure installation spaces, etc., it is practically impossible to provide various drive units for various optical disks. If currently developed RAM-type optical disks come into wide use, disk data recorded by one user may possibly be utilized by another user who owns only a ROM-type drive unit.
Accordingly, there is a demand for drive units that can retrieve data from optical disks of different kinds or standards. It is to be understood that there are similar demands for drive units that can record and erase data in like manner.
Naturally, drive units owned by users who frequently use RAM-type disks for data storage are recording-type drive units that can also retrieve data from ROM-type disks. However, those drive units which are owned by many of users who usually reproduce commercially available software, electronic books, etc., for example, are very likely to be read-only drive units that cannot retrieve data from any other disks than ROM-type disks. Accordingly, a RAM-type disk is expected to be able to fetch data also from drive units for ROM-type disks.
While many of ROM-type optical disks have a plain form such that they can be singly loaded into a drive unit, RAM-type disks are contained in an exclusive cartridge each. In order to retrieve data from a RAM-type disk by means of a drive unit for ROM-type disks, therefore, the RAM-type disk must be taken out of its cartridge. Among currently available RAM-type disks, no one is provided with a cartridge from which it can be taken out. Since a lot of drive units have already been put on the market, it is practically difficult, at present, to change standards for any of disks and standardize the hardware conditions.
Although a RAM-type disk contained in a cartridge can be taken out of the cartridge and loaded into a drive unit for ROM-type disks, data recorded in the fetched disk cannot be accessed unless they are retrieved by means of the drive unit. If a plurality of disks are taken out, moreover, original cartridges in which the disks have been contained individually cannot be discriminated from one another.